**3.3.1 Effect of beating degree and bauxite on dry tensile strength**

Fig.3-3 showed the effect of beating degree and bauxite on dry tensile strength when other factors were held at 0 level. With the increase of beating degree and bauxite, dry tensile strength firstly increased and then slowly decreased, the maximum occurred when the two factors were held at 0 level. The reason was that with the beating degree increased, the fibre sub-wire broom degree was high, the exposure of hydrogen bonding of the fibre surface increased, the bonding forces between the fibres enhanced, so that the film strength increased; when beating degree was more than a certain value, the single fibre strength was destroyed, the bonding force decreased, led to the decrease of strength, adding bauxite excessively to strength had side effect, thus resulting in strength decreased.

Fig. 3-3. Response surface and contour plots for the effects of beating degree and bauxite on dry tensile strength: grammage was held at 80 g/m2 and rosin was held at 0.8%, wet strength agent was held at 1.8%

Study on Manufacturing Technology and Performance of Biogas Residue Film 279

decreased, the maximum occurred when wet strength agent was held at 2%, and bauxite was held at 3.5%. This is because with the adding of the wet strength agent, the adsorption of the fibre system to wet strength agent had already been saturated, and it no longer played a role in increasing strength, anionic trash in absorption system impacted the combination

Fig. 3-5. Response surface and contour plots for the effects of rosin and bauxite on dry tensile strength: beating degree was held at 40SR°, grammage was held at 80 g/m2, wet

Rosin/%

Fig. 3-6. Response surface and contour plots for the effects of bauxite and wet strength agent on dry tensile strength: beating degree was held at 40SR°, grammage was held at 80 g/m2,

Fig.3-7 showed the effect of beating degree and rosin on wet tensile strength when other factors were held at 0 level. When the beating degree was lover than 0 level, wet tensile

**3.4 Effect of interaction factors on wet tensile strength** 

**3.4.1 Effect of beating degree and rosin on wet tensile strength** 

between the fibre, leading to strength decreased.

Dry tensile strenth /N

Bauxite/%

strength agent was held at 1.8%

rosin was held at 0.8%
